Fred Heyworth, 59, shook visibly as a jury at Winchester Crown Court found him guilty of deliberately pouring petrol through the letterbox of the children's home and setting fire to it because his estranged wife was staying there.
"What evil brainstorm prompted you to act as you did we shall never know," the judge, Mrs Justice Steel, said. "This is a tragedy that will remain with you and with others for a very long time. The consequences ... will live with you for ever."
The court was told that Heyworth, of Southampton, Hampshire, had been depressed and angry after his wife, Janette, 22 years his junior, had left him and moved in with her sister, Beverley Good, and Beverley's husband, Melvyn.
Last May, days after describ-ing the Good family as "scum", Heyworth cycled to their home in Sholing, Southampton, carrying a can of petrol which he poured through the letter box. He set fire to it and in the subsequent blaze, Terry, 12, Alison, 10, Nichola, 8, and Patrick Good, 6, perished.
The jury of eight men and three women found him guilty of their murder and of the attempted murder of Mr and Mrs Good and another daughter, Kelly, 15.
Most of the family in the house were sleeping at the time of the attack, but Kelly and Mrs Good saw the petrol being poured through the letter box and were standing on the stairs when the hall became engulfed in a fireball.
The court was told that Heyworth had become obsessed after Janette's departure. On the night of the attack, he had attended a Masonic function at which his wife was working behind the bar. Later, when a card went round for guests to sign he wrote: "Fred Heyworth, single."
He later admitted to detectives that he lit the fire, although he claimed he could remember only going home to bed.
Firefighters, initially beaten back by the ferocity of the blaze, found the bodies of the four children in a back bedroom. The judge said the only comfort was that post-mortem examinations showed they had been killed by fumes rather than flames.
Neighbours had to prevent the distraught parents from trying to get back in the house as Mrs Good screamed for her children. She told police: "The children did not appear, I knew they weren't coming out. I have not got any enemies. I do not know who would want to hurt me and I know my children have never hurt anyone."
After the hearing, a detective said: "The family will never get over this tragedy."
Heyworth, a van driver, told the court he thought the Good family had gone away for the weekend and that the house was empty. "I never ever intended to hurt any children, any adults; it's not in my nature," he said.
However, the court was told that most of the lights and two television sets were on at the time of the attack. In a statement, Mr and Mrs Good and their daughters, Kelly and Andrea, said: "We are pleased that justice has been done. However, no punishment will ever be sufficient for the crime that has been committed. No sentence imposed would ever compensate or end the loss and suffering felt by us all."